Solid wood doors are becoming increasingly rare. Most door manufacturers produce what has come to be know as a "door blank". A door blank has two door skins separated along top and bottom edges by wooded members known as "rails" and along side edges by wooden members known as "stiles". A wooden "lock block" is placed between the skins where a door latch is to be positioned. A cavity between the skins within boundaries defined by the rails and stiles is referred to as a "core" of the door and the material that fills the core is referred to as "coring". The above described components are subjected to a glue pressing process in order to produce a door blank. The most popular type of door blank for interior doors is a "hollow core" door. For exterior doors, insulating foam is injected into the core.
Door blanks manufactured, as described above, are sold to "Prehangers". Prehangers are secondary manufacturers who machine the door blank in preparation for receiving door hinges and latch hardware. The Prehangers bore holes to receive the door latch and machine recesses for placement of hinges. Some manufacturing processes have been developed that produce a door with characteristics that reduce the amount of machining that Prehangers must perform. An example of such a door is U.S. Pat. No. 4,218,848 by Nelson entitled "Plastic Foam-filled Door Having Integral Plastic Housing Defining Lock Cylinder and Lock Bolt Chambers". The Nelson reference discloses a door in which a borehole is premachined through the door skins. The boreholes in the two door skins are then aligned and a plastic lock housing insert is positioned in the borehole prior to the door being subjected to the glue pressing process and the injection of insulating foam coring.
Both interior and exterior doors manufactured through the glue pressing process, as described above, have experienced problems. Interior doors have a problem with delamination, where the door skin comes away from one of the rails or stiles as a results of glue failure. They are also prone to warp when subjected to climactic changes. Exterior doors are subject to moisture infiltration in the area of the lock latch. In cold climates this causes the lock latch to freeze and fail. In moist climates this results in warpage of wooden skins and rusting of metallic skins. Warpage can also occur in exterior doors due to temperature differentials, for example when it is 70 degrees fahrenheit indoors and minus 30 degrees fahrenheit outdoors.